DUBAI, United Arab Emirates (AP) ― Somali pirates hijacked a supertanker hundreds of miles off the Horn of Africa, seizing the Saudi-owned ship loaded with crude and its 25-member crew, the U.S. Navy said Monday.

It appeared to be the largest ship ever seized by pirates.

After the brazen hijacking, the pirates on Monday sailed the Sirius Star to a Somali port that has become a haven for bandits and the ships they have seized, a Navy spokesman said.

The hijacking was among the most brazen in a surge in attacks this year by ransom-hungry Somali pirates. Attacks off the Somali coast have increased more than 75 percent this year, and even the world's largest vessels are vulnerable.

The Sirius Star, commissioned in March and owned by the Saudi oil company Aramco, is 1,080 feet long -- about the length of an aircraft carrier -- making it one of the largest ships to sail the seas. It can carry about 2 million barrels of oil.

Lt. Nathan Christensen, a spokesman for the U.S. Navy's 5th Fleet, said the pirates hijacked the ship on Saturday about 450 nautical miles off the coast of Kenya -- the farthest out to sea Somali pirates have struck.

By expanding their range, Somali pirates are "certainly a threat to many more vessels," Christensen said. He said the pirates on the Sirius Star were "nearing an anchorage point" at the Somali port town of Eylon Monday.

Somali pirates have seized at least six several ships off the Horn of Africa in the past week, but the hijacking of a supertanker marked a dramatic escalation.

The pirates are trained fighters, often dressed in military fatigues, using speedboats equipped with satellite phones and GPS equipment. They are typically armed with automatic weapons, anti-tank rockets launchers and various types of grenades.

With most attacks ending with million-dollar payouts, piracy is considered the most lucrative work in Somalia. Pirates rarely hurt their hostages, instead holding out for a huge payday.

The strategy works well: A report last month by a London-based think tank said pirates have raked in up to $30 million in ransoms this year alone.

In Somalia, pirates are better-funded, better-organized and better-armed than one might imagine in a country that has been in tatters for nearly two decades.

They do occasionally get nabbed, however. Earlier this year, French commandos used night vision goggles and helicopters in operations that killed or captured several pirates, who are now standing trial in Paris. A stepped-up international presence of warships recently also appears to have deterred several attacks.

The Sirius Star was sailing under a Liberian flag. The 25-member crew includes citizens of Croatia, Britain, the Philippines, Poland and Saudi Arabia. A British Foreign Office spokesman said there were at least two British nationals on board.

An operator with Aramco said there was no one available at the company to comment after business hours. Calls went unanswered at Vela International, the Dubai-based marine company that operated the ship for Aramco.

Classed as a Very Large Crude Carrier, the Sirius Star is 318,000 dead weight tons.

Raja Kiwan, a Dubai-based analyst with PFC Energy, said the hijacking raises "some serious questions" about what is needed to secure such ships on the open seas.

"It's not easy to take over a ship" as massive as oil tankers, which typically have armed guards on board, he said.

But pirates have gone after oil tankers before.

In October, a Spanish military patrol plane thwarted pirates trying to hijack an oil tanker by buzzing them three times and dropping smoke canisters.

On April 21, pirates fired rocket-propelled grenades at a Japanese oil tanker, leaving a hole that allowed several hundred gallons of fuel to leak out, raising fears for the environment.

In September, three pirates in a speed boat fired machine guns at an Iranian crude oil carrier, though the ship escaped after a 30-minute chase.

Warships from the more than a dozen nations as well as NATO forces have focused their anti-piracy patrols in the Gulf of Aden, increasing their military presence in recent months.

But Saturday's hijacking occurred much farther south, highlighting weaknesses in the international response.

Graeme Gibbon Brooks, managing director of British company Dryad Maritime Intelligence Service Ltd, said the increased international presence trying to prevent attacks is simply not enough.

"The coalition has suppressed a number of attacks ... but there will never be enough warships," he said, describing an area that covers 2.5 million square miles.

He also speculated that the crew of the Sirius Star may have had a false sense of security because they were so far out to sea.

He said the coalition warships will have to be "one step ahead of the pirates. The difficulty here is that the ship was beyond the area where the coalition were currently acting."